Variable pitch propeller



March 4, 1952 c. R. SACCHINI 2,588,166

VARIABLE PITCH PROPELLER Filed March 1, 1946 7 SheetsSheetvl /N VEA/TOPMarch 4, 1952 c. R. SACCH'INI VARIABLE PITCH PROPELLER Filed March 1,1946 7 Sheets-Sheet 2 nvvavroe COLl/M5U5 e j/ICCH/N/ ATTOP/VEY March 4,19 c. R. SACCHINI VARIABLE PITCH PROPELLER Filed March 1, 1946 7Sheets-Sheet 3 Q INVENTOP C01. W505 la jACCH/N/ March 4, 1952 c. R.SACCHINI VARIABLE PITCH PROPELLER 7 Sheets-Sheet 5 Filed March 1, 1946will OMN

lNVE/VTOP COLUMBUJE 5/4CCH/N/ Arrog/vfy March 4, 1952 c. R. SACCHINI2,588,166

VARIABLE PITCH PROPELLER Filed March 1, 1946 7 Sheets-Sheet 6 INVENTOPCOLUMBUS e JAcc/v/N/ HTTOP/VEY March 4, 1952 c. R. SACCHINI VARIABLEPITCH PROPELLER 7 Sheets-Sheet '7 Filed March 1, 1946 7 w m 6 9 7 0 Z mZ 2 7 3 a zze 2 1 FIG. /2

4% ATTORNEY FIG. 11

Patented Mar. 4, 1952 UNITED STATES 2,588,166 VARIABLE PITCH PROPELLERColumbus R. Sacchini, Willoughby, Ohio, assignor to The Marquette MetalProducts Company, Cleveland, Ohio, a corporation of Ohio ApplicationMarch 1, 1946, Serial No. 651,278

5 Claims. (01. 170-16931) This invention relates to a variable pitchpropeller mechanism and particularly to a mechanism provided with fluidpumping and servomotor means connected with the blade or blades to beadjusted, which pumping means is operated as 5 a consequence of rotationof the propeller.

The general object is to provide an improved hydraulically operatedcontrollable pitch propeller.

Another object is to provide an improved hy- 1 draulically operatedcontrollable pitch propeller in which the operating fluid is containedin a sealed system rotatable with the propeller, characterized in thatno matter how full of fluid thesystem is, no part of the fluid controlmech- 1 anism can thereby be restricted against free operation.

Another object is to provide, in a hydraulically actuated controllablepitch propeller, an improved means for preventing the blade or bladesfrom 2 being moved out of adjusted position by forces opposing the pitchadjusting mechanism of the propeller, and specifically to provide animproved hydraulically-acting anti-creep mechanism for the blade orblades. 2

A further object is to provide, in a hydraulically operated controllablepitch propeller, an improved means for controlling, independently of thespeed of rotation of the propeller, the rate at which the blades areadjusted.

A further specific object is to provide a simplifled fluid actuatedmechanism for initiating the operation of a blade pitch adjusting means.

A further object is to provide an improved hydraulically actuatedselectively operable mechanism for causing initiation of operation of ablade pitch changing mechanism of a propeller.

A further object is to provide, in a hydraulically operated propeller, ablade pitch control system which includes a releasable pitch limitinglatc H rendered operative in part by fluid in a hydraulically operatedactuating system separate from the pitch adjusting mechanism, means toenable the actuating mechanism always to be operated instantly to a fullfunctioning position where it is retained until the pitch limiting latchhas been operated in a manner to permit blade adjustment to an abnorma1pitch setting.

A concomitant object is to provide an improved means for enabling alatch-release-actuating hydraulic mechanism to be moved quickly manuallyinto a self retaining position so as to store energy for subsequenthydraulic operation.

A further object is to provide an improved manually operable hydraulicactuator for an oppositely acting blade pitch adjusting mechanism of apropeller, which actuator is self centering to neutral position uponrelease of manually applied force.

Other objects and features of the invention will so become apparent fromthe following description of the illustrative forms shown in thedrawings, wherein:

Fig. l is a longitudinal assembly sectional view in a vertical plane ofa propeller mechanism of the three-blade type;

Fig. 2 is a view partly in section as indicated by the line 2-2 on Fig.1 and showing, in elevation, the preferred hydraulic actuator mechanism;

Fig. 3 is a schematic assembly view showing the fluid supply, pumpingmechanism and part of the hydraulic actuator system in one form;

Fig. 4 is a central longitudinal sectional view of one of two fluidcontrol units shown schematically on Fig. 3;

Fig. 5 is a fragmentary central sectional view of a fluid control unitsimilar to that shown by Fig. 4, provided for control of the pitchlimiting latch mechanism;

Fig. 6 is a detail sectional view as indicated at 6-5 on Fig. 4, showinga typical shape of valve plungers used in the fluid control units;

Fig. 7 is a schematic partial assembly view similar to Fig. 3, butshowing a somewhat modified arrangement of fluid control mechanism;

Fig. 8 is a view similar to Fig. 4, showing more in detail part of themodified construction according to Fig. '7;

Fig. 9 is an elevational view of the unit similar to Fig. 8, shownpartly in central section;

Fig. 10 is a vertical sectional view of the main hand pump or actuatorportion of the mechanism shown at the right in Fig. 2;

Fig. 11 is a sectional detail view taken as indicated at |I-ll onFig. 2;

Fig. 12 is a detail sectional view taken along the plane indicated atl2-l2 on Fig. 11, and

Fig. 13 is a detail sectional view taken at l3-I3 on Fig. 10.

Referring further to the drawings, Figs. 1 to 5 inclusive, the assemblyshown by Fig. 1 shows a propeller mechanism I including a central hub 2,formed as a hollow steel forging with a spheroidal central portion 3 andparallel annular front and rear .end flanges 4 and 5. The forgingincludes equally spaced radially extending barrel portions 6, one beingshown, for supporting blade assemblies such as]. Each barrel portion 6contains suitable bearings enabling the blade assembly to be rotatablyadjusted in opposite directions for forward pitch in a normal pitchrange, further adjusted forwardly for feathering and reversely adjustedbeyondnormal low pitch as for braking.

The hub 2 is mounted on a central hub carrier 8, suitably secured as bya key 9 to a, tapered portion oi an impeller shaft III. A sleeve-likenut engaging threads on the forward end of the shaft further secures theshaft to the hub carrier. J A pitch adjusting 'servomotor M has a whousing or block l2, partly surrounding the sleeve portion |3 of the nutII, and appropriately secured to the hub as against the forward flange 4thereof.

Journalled between the forward portion of the hub carrier 8 and theservomotor block l2 (partly supported by both) is a master pitchadjusting gear element l5, having gear teeth "i in mesh with teeth ofrespective tubular por-' tions ll of the blade assemblies. Each tubularportion I! has a pilot bearing at |8 on the hub carrier.

The mechanical parts of the servomotor M comprise identical butrelatively oppositely acting pistons and 20' in cylinders 2| and 2|respectively carried in the motor block I2. Each piston 20 has rackteeth 22 in constant mesh with.

gear teeth 23 on the forward sleeve portion of the gear l5, so that asthe pistons are reciprocated the blades are adjusted through the masterable flller opening, not shown, and is suitably sealed off from thehollow interior of the hub forwardly from the sump and also sealedaround the central portion of the hub carrier and impeller shaft. 'Thewalls forming the sump chamber thus rotate with the hub whenever the propeller is turned by the shaft l0.

Behind the closure plate 26 of the sump is a fixed, that isnonrotatable, framework 28 providing a generally closed chamber 29peripherally sealed as by the telescoping joint assembly 29 (top,Fig. 1) so that the chamber 29 may retain suitable lubricant for a fluidcontrol actuator cam mechanism to be described and contained in thechamber 29. Fluid supplied from the sump chamber is selectively pumpedto oppositely operating portions of the servomotor M by one.

or the other of two hydraulic control (pumping and valving) units ofsubstantially identical form indicated at 30 and 3|, Fig, 3. A pumpplunger 340i the unit 30, through suitable communicating lines partlyindicated at 32,;supplies the pressure chambers P and PI of theservomotor and the pump plunger of the unit 3|, through a communicatingline diagrammatically indicated at 33," supplies the pressure chambersP2 and P3 of the servomotor.

The hydraulic control units 30 and 3| alsocontain exhaust valvemechanisms generally indicated at 36 and 31. The exhaust valvemechanisms are operated in timed relation to the operation of the pumps34 and 35 in such a manner that when, for example, the pump 34' suppliesfluid to the servomotor chambers P and PI, the exhaust valve mechanism31 is operated to vent used fluid from the servomotor spaces P2 and P3to the sump; and when the pump 3'5 of unit 3| is operated, the exhaustvalve' mechanism 38 of unit 30 operates to vent fluid from chambers Pand PI.

A pitch limiting mechanism generally indicted at 40, Fig. 3 only,cooperates with an element of the servomotor mechanism normally to limitpitch adjustment of the blades in either direction within a rangesuitable for forward driving and, abnormally, to limitpitch adjustmentbeyond that range in opposite directions. As shown, a

4- 0 servomotor or plunger 4| of the pitch limiting mechanism operatesin a suitable cylinder 42 and has a latch portion 43 normally seated ina recess 44 in, for example, the piston 20.

In the actual design (not shown) the latch 43 cooperates with steppeddepression in the forward face of the gear l5, the plunger 4| beingmounted in the pitch adjusting servomotor ho -.sing l2.

The normal pitch limits are established by abutments 45 and 46 definingparts of the depression 44; and beyond those abutments, in respectivedirections of movement of the piston 20, are spacesdefined in part bylimiting abutments 41 and 48. The plunger 4| is withdrawn to theillustrated position, against the force of a return spring {-49, byfluid forced by a pumping unit generally indicated at 50, mounted on thehub carrier and operated essentially the same as are the units 30 and3|. The pump plunger 53 of the unit is connected with a pressure chamber5| of the latch plunger 4| by a suitable conduit represented insimplified form at 52, Fig. 3. T..c

fluid forcing unit 50 is controlled at the will of the operator towithdraw the latch plunger menber 43 from thevdepression 44 whenever itis desired to effect reverse pitch as by movement of the piston 20beyond the latch abutment 48 in the direction toward the abutment 48 andalso whenever it is desired to move the piston in the. oppositedirection past the abutment 45 for feathering.

Reference may be had to an application of Gordon W. Hardy, 629,539,filed November 19,

1945, now Patent Number 2,515,037, issued July. 11, 19,50, and owned bythe assignee hereof, for,

constructional details of a mechanism corresponding essentially to thatthus far described and which details are not referred to herein.

The pump plunger 53 of the latch control unit 50 and the pump plungers34 and 35 each has an operating stem projecting out of the sumprearwardly for operative contact with a respective manually settable camin the chamber 29.

- The exhaust valves 36 and 31 have operating stems similarly arranged,all the stems terminating rearwardly in the same plane.

The stem 540i the plunger 53 makes contact with the intermediate one ofthree concentric ring cams 55,.56and 51. The cams are hinged formovement toward and away from the propeller hub on respective pivot pins58 near the bottom of the chamber 29 and supported by the framework 28.With that arrangement, the upx. portion of each of the cam rings can bethrust rwardlyat the will of the operator to cause energization of thepumping systems and operation of theexhaust valves. In Fig. 3 theintermediate cam member 55 has been thrust forwardly to cause release ofthe pitch limiting latch plunger 4 |-43of pitch adjusting mechanism andthe outer ring 5l' has ben thrust forwardly to cause reciprocations ofthe pumping element 34 of the unit 30 and cooperating opening movementsof the exhaust valve 37 of the unit3|. Those operations have resulted inmovement of the piston 20 toward reverse pitch and beyond the normalpitch limiting abutment 46 with respect to the latch 43.

If, instead of the ring cam 51, the ring cam 56 is thrust forwardly,assuming the other two cams 55 and 57 are retained in their rearwardnonoperating positions (latch 43 seated in depression 44), the operationwould be an actuation of the pump plunger-35 of unit 3| and valvemechanism ment of the piston 20, then the piston 20 would be free tomake the necessary traverse of the latch 43 to enable feathering and thefeathering operation would terminate when the latch element 43 engagedthe abutment 41.

The selective operation of the ring cams 55, 56 and will be more fullydescribed later, but for the moment it may be noted in reference to Fig.2 that, with an actuator handle 60 in the position in which it is shown,hydraulic fluid is forced through a line 56a to a servomotor of avertically sliding cam 56b, causing operation of the innermost ring cam56 on the pump 35 of the unit 3| and exhaust valve 36 of the unit 30,thus causing forward pitch adjustment of the blades. With the handle 00in a reversed position as indicated by broken lines at 60c, Fig. 2,actuator fluid is supplied through a line 57a to the servomotor of a cam511), thus causing the operation of the pump plunger 34 and the exhaustValve mechanism 3'! of units 30 and 3i respectively so that the bladesare moved toward low pitch or reverse positions. Actuation of theintermediate cam ring 55 is accomplished by a movement of a separateactuator handle BI, Fig. 2, from the position in which shown through180, causing actuating fluid to be fed throu h I a line 55a to aservomotor of a cam 551), thus to move the latch element 43 from betweenthe abutments 45 and 46.

Referring particularly to Fig. 4, wherein one of the fluid cont ol units30 and 3| is illustrated in detail, it will be noted that said unitcomprises a generally cylindrical bodv adapted to fit and sealinglyclose an opening in a forward wall of the sump chamber at a peripheralflange I2 of the body. Another flange 73 of the body makes peripheralsealing contact with the rearward wall 21 of the sump chamber so thatonly the reduced diameter space '14 between the two flanges cancommunicate with the sump through suitable ports in the body. The pumpplunger 35 is mounted in a sleeve having an inlet port II communicatingwith an ali ned port in the wall of the body 70 leading to the sump. Aspring 6 in a bore 17 of the body forces the plunger 35 toward the ringcam 56 to the inoperative position shown on both Fi s. 3 and 4.Reciprocation of the pump by the ring cam 56, Fig. 3,

causes movement of fluid trapped in the pump chamber space l8 throu h across passage I9 to a check valve plug 80 disposed centrally of the bodyI0 and slidable in an axial bore 8! of said body. The preferred crosssectional shape of the check valve plug is as shown by Fig. 6, i. e.non-circular to allow fluid to pass the plug. The valve 80 preferablyhas a ring seal 82 closing against a flat rearward face defining part ofthe bore BI, which face is centrally ported axially of the body forcommunication with the cross passage 79. A fairly light weight returnspring 84 operates the valve plug 80 to cause the ring seal to closesaid central port whenever the pump plunger 35 ceases to move to theleft as illustrated on Fig. 4.

The fluid pumped past the check valve 80 passes through the central boreof a fitting 85 to the delivery line 33, formed partly in the fitting,but said fluid is also free to flow through a cross passage 06 to thecentral bore 81 ofan 6 exhaust valve sleeve 88, sealingly fitting aneccentric bore 89 in the body I0. Exit of fluid from the bore 8'! isnormally prevented by a valve plug 90 similar to the plug and guided bythe bore 81. The plug has a ring seal 9I closing a port 92 formed in awall 93 of the sleeve 88 intermediate the ends of said sleeve. Theringseals 82 and 9| are of similar construction, being secured to therespective plug members 80 and 90 by respective screws 95 and 96 havingtapered or flared heads. The flared head of the screw 96 has anon-circular stem or extension 9'! integral therewith which projectsslidingly through the port 92 but does not seal said port. The port 92communicates with a chamber I00 in the rearward end of the sleeve 88 andwhen once the ring seal 9| is moved off the valve seat around the port92 against the pressure of a return spring IOI in the sleeve, fluid isfree to flow from port 92 past a non-circular land I92 of a valveoperating plunger I03. The plug element 90, seal 9|, stem 96 and thevalve operating plunger I 03 constitute the moving parts of the exhaustvalve mechanism 31. The plunger I03 is sealed as at I04 against exit offluid from the rearwardly open bore of the sleeve 88, but rearwardlyfrom the non-circular land I02 of the plunger I03 the sleeve and bodyare formed to provide an outlet port at I05 leading to the sump. Thenoncircular stem 97 of the exhaust valve plug 90- operates in advance ofthe cooperating pump plunger 34 or 35 of the other unit; while the otherexhaust valve operates in trailing relation to its cooperating pump.When the two valve stems 91 are of proper length for abutment by thebottom of the socket I03a of the associated plunger I03, the exhaustvalves and pumps are in phase. Hence, it is merely necessary to selectthe proper length of stems 9'1. Alternatively adjustable abutments (notshown) can be provided between the stems 9i and sockets I 03a, whichabutments would be set and locked prior toassembly of the propellermechanism.

Additionally, for protecting the hydraulic mechanism against damage byoverpressure after the latch 43 has engaged one of the abutments 45-43,the body I0 is provided with a relief valve communicating with the crosspassage 19 and preferably located coaxially of the check valve 80 in arearwardly open bore I08 of the body 10.

diameter central portion of the exhaust valve plunger I03.

In operation, the pulsations of the pump plunger 35 cause movement offluid through the conduit 32 to operate the servomotor pistons 20- and20' to the desired positions or until the pistons are stopped byrelative abutment of the pitch limiting latch mechanism elements. Aftersuch relative abutment any further operation of cras es-r:

theL-pump plunger causes movement of the relief valve plunger I09 to.the right, Fig. 4, dumping excess pressure fluid to the sump chamber25. To .exhaust fluid from the servomotor M, the plunger I33 of the unit39 is operated by the appropriate ring cam, said plunger I93 of unit 30abutting the stem 9'! of the associated valve plug assembly (90, 9?),thus opening the valve and allowing fluid to move through the line 33 tothe sumpchamber. Due to the non-circular cross section of the stem 91 ofthe exhaust valve plug 90; there is no pocketing of fluid within thecentral bore of the actuating plunger I03 in which the stem slides.

The pump portion 53 of the latch release control unit 53. is the sameas'that already described in connection with Fig. 4 and it will be notedin Fig. 3 that a counterpart of the check valve 80 is provided as at H5ahead of the delivery line 52' leading to the latch release plungerchamber 5If.' Also, the unit 59 has a relief valve II6 to prevent damageto the latch mechanism upon over-delivery of fluid by the pump 53. Therelief valve H5 is identical with relief valve I09, III, Fig. 4.

Venting of operating pressure from the latch plunger chamber 5I (Fig. 8)after the release of the latch has been accomplished requires only ableed-off operation. As shown at the upper right in Fig. 5, a fixed plugI I8 corresponding in position to the exhaust valve plunger I03, isseated in the rearward portion of a sleeve I IS. The plug H8 is formedwith a central necked portion terminating rearwardly at an enlarged headI28, sealing the rearward end of the sleeve I I9 behind an exhaust portI2I leading to the sump chamber. Fcrwardly from the port I2I arelatively smaller diameter enlargement I22 of the plug I I8 occupiesthe central bore of the sleeve H9 and provides a peripheral gap I23around the enlargement I22 and within the sleeve. The gap may be on theorder of a few thousandths of an inch radial width to provide arestricted orifice for passage of fluid from the port I24 wh ch is opento communication with the delivery line 52 as shown by Fig. 3. Theforward end of the plug II 8 has a groove I25 across the face of theplug which rests against the partit on I25. Thus, whenever the pump 53of the latch release control unit 50 is operated, the latch 43 iswithdrawn from position necessary to make contact with either latchabutment 45 or 46, and the restriction at I23, Fig. 5, blocks returnmovement of the latch to init al position temporarily only. When thepump 53 is caused (by the operation of the mechanism throughmanipulation of the actuator handle iiI, 2) to cease operation,

then the operating fluid for the latch plunger is bled from the supplyconduit 52 and the connecting passages to the sump chamber through therestricted orifice I23 and the latch is returned to its initialforwardmost position by the spring 49. Said spring forces the actuatingfluid past the restricted orifice.

It will be seen from comparison of Figs.-

leading from the servomotor M are filled withfluid, the operation ofopening the exhaust. valve will be blocked because hydraulic fluid issubstantially incompressible. Also, after either pump plunger 34 or .35on its pumping stroke has closed its associated inlet port II andassuming the cooperating exhaust valve has been opened, a completecharge of fluid in the sump chamber 25 and communicating passagesleading to the then exhausting cylinder chambers of the servo motor Mwill block further. movement of such pump plunger. In actual practice,with a similar system it was found that it was impossible to fill thesump chamber entirely with operating fluid because, until such time assome of the charge had been forced or bled out of the system, the camrings could not be moved to exhaust valve and pump plunger operatingpositions. To overcome that difficulty, a readily compressible elementI30 is placed in the sump chamber 25. In the mechanism shown by Figs. 1and 2, the compressible element is preferably in the form of a tubularelastic ring formed either as a single length of tube sealed at bothends or as an endless ring. Said element could be of any other desiredshape. A suitable material for the ring I30 is synthetic rubber. Thering lies outwardly from all the pump and valve units 30, 3| and 59 asagainst the inner surface or" the radially outward wall of the sumpchamber.

In order, independently of the speed of rotation of the propeller, togovern the rate at which pitch adjustment is effected by operation ofthe pump plungers 34 and 35, each of the feeding and exhausting conduits32 and 33 is provided with a suitable needle valve with a restrictedorifice (not shown).

Conventional needle valves are represented at I32 and I33 respectivelyin the lines 32 and 33. Those valves are not adapted or intended to beadjusted during flight. Since the strokes of the plungers 34 and 35 areof a length determined by the set or adjusted positions of the cam rings5'5 and 57 and that may be varied by the operator and the speed ofreciprocation of the pump varies according to propeller speed, the rateof fluid delivery to the servomotor chambers P, PI, etc. wouldordinarily vary greatly. By restricting the passage of fluid from thepumps to the servomotor, the rate can be controlled at a valueconsiderably less than the maximum capacity of the pumping mechanisms.vIn event the propeller is rotating above the speed required for cruisingspeed, for example, the pumps will tend to de-. liver fluid at greaterthan the desired rate and.. in that event, the over-delivery will bereturned .plungers are in position to open the fluid inlet ports I6, isprevented by the check valves -82, Fig. 4.,

Referring to the arrangement according to Figs. 7, 8 and 9, these differfrom the construction described above principally in that anticreepvalve mechanisms are provided and the mechanically. "opera-ting exhaustvalve mechanisms. are omitted. The cam ring 56,.Fig.-7, operates onlythe pump plunger 35a corresponding to the plunger 35 of Fig. 3 and thecam ring 51 operates only the pump plunger 34a which corresponds to theplunger 34 of Fig.4. The cam ring 55 has exactly the same function asdescribed in connection with Fig. 3, namely, to operate the pump plunger53a of the pitch limit latch release mechanism. The fluid delivery andexhaust lines 32 and 33 are identical with the previously describedconstruction. The servo portion of the latch release mechanism is thesame as previously described and the cam rings are or may be adjusted aspreviously described above, through the servomotor portions of themanual actuating mechanism (right, Figs. 1 and 2).

Referring especially to Fig. 8, attention is called to the two-partplunger arrangement I35 which replaces the single piece pump plungers 34and 35 of Figs. 3 and 4. The plunger member I35 slidably seals thecylinder sleeve I36 at the rear-- ward end of the sleeve and the forwardend of said sleeve is open at I 31 for communication with the interiorof a central bore I38 of the body 3Ia, corresponding to the body 3| ofFig. 4. The body 31a is generally the same as the bodies 36, 3I and '56already described. An inlet port 1Ia leads from the annular space 14 ofthe body 3I a to the interior of the sleeve I36 and is initially open atboth sides of a sealing land or relatively enlarged portion I40 of theplunger member I35- Behind the land, the plunger member has crosspassages at I4I communicating with a central forwardly open socket I42of the plunger. Rear- Wardly from the cross passages I4I the plungermember I35 is slidably sealed against the inner wall of the sleeve I36as by a ring seal I43. In the fully retracted or rearmost position ofthe plunger I35, fluid is free to pass from the sump chamber 25, throughthe cross passages 1Ia to an annular space I44 around the forward end ofthe plunger member I35 and within the sleeve I36, thus to charge thepump. As the plunger member is thrust forwardly by the cam ring 56, theland I46 seals off the passage 1Ia so that the fluid occupying the pumpsleeve is forced through the passage I31. The return stroke of theplunger member I35 may be accomplished by a fairly light spring 16a ascompared to the high rate return spring 16 of Fig. 4 because returnmovement of the plunger member I35 is; in the Fig. 8 arrangement,unrestricted by vacuum after the check valve (to be described) at thedelivery end of the unit 3m closes.

The vacuum breaker arrangement includes a check valve plug I46 whichacts to admit low pressure fluid freely to the annular space I44 throughthe rearward inlet passages MI and I42 of the member 535 on the returnstroke of the pump plunger. The plug I46 is held in sealing position bya light spring I41 bearing at one end against an end wall portion of theplug I46 and at the opposite end against a perforated disc I48 withinthe pump plunger 135. The disc is held in position against a shoulderI49 of the pump plunger by the force of the spring 16a which ismaterially greater than the force of the return spring I41 oi the vacuumbreaker valve.

It will be seen that during return movement of the pump plunger memberI35, the vacuum breaker valve I46 is free to move forwardly to openposition (to the left) within the plunger member; Wherefore, until theforward edge of the land I46 has moved rearwardly to open the inletpassage Ha to the pressure chamber ahead of thepump plunger assembly,fluid isfreeto passage 1Ia, cross passages MI and socket.l42

to the pressure chamber of the pump.

The fluid delivered. by the pump to the passage I31 travels by way ofthe central bore I38 in -a space provided by a reduced diameter portionI56 of a valve sleeve I5I. The sleeve I5I is held in fixed position bythe fitting 85a to which the delivery duct 33 is connected. Said sleevehas land portions at I52 and I53 tightly fitting the bore I38. Thesleeve I 5| has a central smooth bore I 54 from end to end and arearward portion of the sleeve ahead of the land portion I53 is openedby way of cross passages I55 to said smooth bore I54. Within the bore I54 is slidably mounted a piston assembly I55 which forms the mainportion of the anti-creep valve mechanism. The same valve mechanismfunctions for exhaust of fluid from the pitch adjusting servomotor.

The anti-creep and exhaust valve piston assembly I55 includes a spoolshaped body member I56 having lands I51 and I58 at its rearward andforward portions respectively, slidably fitting the central bore I54 ofthe sleeveI5I. It is only necessary that the land I51 be especiallyprovided for sealing said bore I54 and ring seals I59 are provided forthat purpose. Between the. two

lands of the piston body member I56, the latter has a reduced diameterportion I66 with cross passages at both ends of said portion. Theannular space thus provided around the piston body member communicateswith the interior axial main bore I6I of said member. The bore I6Iterminates rearwardly in a reduced diameter bore portion I62 so as toform a check valve seat for a valve plug I64 which is closed against theseat by a light spring I65. The fluid'forced by the pump to the interiorof the sleeve I 5| through the cross passages I55 forces the check valveplug 564 off its seat and then passes through the main bore IM to theoutlet fitting 85a. The

check valve plug I64 normally retains the fluid forced by the pump.

The piston body I58 is held in the illustrate position against thefitting a by a relatively strong spring I 66 seated in the bottom of thebore 538 aganist a plug element I61. The plug has a stem with a reduceddiameter end portion I66 extending into the bore I62 of the plunger #56in position to move the relatively small diameter check valve plug I64off its seat whenever return pressure in the delivery line leading tothe servomotor exerts sufiicient pressure on the piston to overcome thespring I66 and move the piston assembly rearwardly or to the right asillustrated in Fig. 8. Then the stem portion I58 engages the rearwardend of the check valve plug I64 and unseats said plug. Thereupon, returnpressure in the delivery line 33 bypasses the check valve I64 andescapes from the valve body 3m by way of the pump plunger cylindersleeve I36 and the then retracted pump plunger member I 35. The pressuremaintained by the spring I66 is predetermined in accordance withwhatever force it takes to hold the blades from being moved out ofadjusted position by counter pressure on the blades.

The operation of the anti-creep valve mechanism for servomotorexhausting purposes is the same as described above. The pump pressure ofunit 36a overcomes the pressure of the spring I68 of unit 3| a and viceversa for exhaust.

In the event operation of either pump 34a or 35a, Fig. '1, is continueduntil the latch plunger slides.

masseuse l3-iengages one ofthe pitchlimiting stops described inconnection with Fig. .3, the over-delivery of the pump is'ventedfrom theunit 30a 01' 31a to the sump through a respective relief valve' assemblyI'IO, Fig. 8, the construction and operation of which is essentially thesame as that of the relief valve I09-III of Fig. 4. To

' communicate the annular space around the sleeve fI5I with the reliefvalve, a portion of the cross 'passage I3'I designated I3'Ia leads to anoutlet bore I'II in a valve sleeve I12. The relief valve bore I14 of thesleeve I12 in which the plug The'main body of the unit 3Ia has an outletpassage at I16 for communicating the interior of the sleeve I-I2 withthe sump. The return spring for the relief valve plug has usually nearlytwice the rate of the anti-creep valve spring I66.

' The. anti-creep valve mechanism of Fig. 8 is not needed for thecontrol unit 50a of Figs. '7

and 9 which controls the pitch limiting latch operating servomotor. Arestricted orifice for exhausting fluid from the latch release controlsystem (line '52 etc, Fig. 7) is needed and that can easily be providedby removing the sealing rings 159 from the rear land of the pistonmember I56a as shown by Fig. 9. The annular gap I" (Fig. 9) between thepiston land I5! and the inner bore of the sleeve I5I serves as thebleed-oil aperture for the latch operating servo 'system.

The valve construction according to Fig. 8 may bemodified so as toemploy the compressible ring seal closures and flat valve seats such asprovided'for the valve plugs 80, 90 and I09 of Fig. 4. "Inother words,in Fig. 8 the anti-creep valve 'plug 184 and the relief valve plug I10may be "made-with appropriate recesses for ring type seals, held inplace as by flared head screws and closing against flat valve seats.Such construction greatly reduces the time required to machinethe valveseats, since the ports closed by "the compressible ring seals do nothave to be aligned accurately with the guide bores for the plugs.Moreover, centrifu al force acting on the fiat seat-engaging valve plugsof Fig. 4 never affects the sealing operation, even though the valveplugs have considerable lateral clearance 'inthe guide bores. In'thetype of valve plug em- A further advanta e of the :less apt to causefaulty valving operation.

Attention 'is'called to the fact that it is un-'- necessary in the fluidcontrol units according to .Figs. 4; 5, .8 and 9 to seal the rear endfaces of -the'main"unit bodies against the back closure plate 26,Fig. 1. That feature is of special importance inxconnection with therelief val es I09, Fig. 4, and corresponding reliefvalve I10 of'Fig. 8.The rearwardly open bores in the unit bodies which receive thevalve'plug assemblies are plugged by positively acting compressed linearseals so that when the valve assemblies aresubjected' .to sufiicientlyhigh pressure to open therelief valve plugs there is never anylikelihoodof loss of'fluid from the sealed hydraulic system as along theoperating stems of the 'ring cam actuated parts.

' cylinder sleeve of the cylinder sleeve.

Referring further to the ringucam actuating mechanisms shown by Figs. 1and 10 to 13inelusive, the. sliding cams b, 56b and 5112 are mounted onthe framework 28 in suitable guides and each hasa bevelled lower endportion I80 (one shown in Fig. l) which, through contact with anadjacent bevelled rear surface of the associated ring cam; thrusts theselected ring cam forwardly into pump or valve actuating position withrespect to the control units 30, 3!, 50, etc. as already described. Eachof the sliding cams has an arm portion at its upper end as at I8I, Fig.l, whichv is normally forced downwardly by a spring I82 to hold thesliding cam in inoperative position. Adjustable limit stops for thesliding cams may be provided on the framework 28in position to engagethe upper ends of the sliding cams. To operate the sliding cams, eacharm I 8I overhangs a respective servomotor plunger orpiston I83 in asuitable cylinder bore of the framework 28. The actuator feed lines 55a,56a and 51a communicate with the cylinders of respective pistons I83 insealed relation thereto.

Referring to the actuator pump mechanism of Figs. 10 to 13 inclusive,the lines 55a and 51a are'supplied by oppositely disposed pump pressurechambers I85 and I8! in a common housing I88 having fittings I90 and I9Iconnected to the respective feed lines 56a and 51a, Fig. 2, and alsoacting as sealing plugs for the outer ends of the chambers I86 and I81.A common I92, Fig. 10, is fitted tightly into a horizontal bore I 93 ofthe housing I88. The end fittings I90 and IOI have ring seals I94 andI95 pressed against the re pective ends The pressure chambers I86 andI81 are each open to communicate with a common supply chamber I96 forreserve fluid preferably formed in the housing I88 above the cylindersleeve I92. Vertical ports I 98 and I9! formed in the cylinder sleeveand housing I88 communicate the respective pressure chambers headportions 202 and 203 suitably sealed against a the wall of the cylindersleeve.

The land portions, in the illustrated neutral or inactive position ofthe piston, are so disposed that both supply passages I98 and I99 areopen. The piston is held in the centered neutral position by fairlystrong springs 204 and 205 of equal length and scale. The springssurround reduced diameter extensions 206 and 20'! of the piston and bearoppositely upon shoulders adjacent the piston heads and may be seated attheir opposite ends'in respective socket portions of the plugs I andI9I.

Inorder to use a single piston for supplying fluid selectively to thefeed lines 56a and 51a, it is necessary to provide a fluid bypass fromone pressure chamber to the other in order that return of the piston tocentered position will not be blocked 'by vacuum in the last activepressure chamber. The bypass is formed as a central axial bore 208 inthe piston 200, said bore terminating in respective counterbores 2H) and2H within the reduced diameter extensions 286" and 201. The counterboresprovide check valve guides for valve plugs, each in the form of a metalball as indicated at 2I2 and 2I3, slidably fitting the guides. Thepiston extensions 206 and 201, Figs. 10 and 13, have slots as at 228'and 229 leading from the outer ends of the extensions pasttheballs'sothat fluid :from the I 203 cuts 01f the supply passage I99.

the bore 208 out of contact therewith for its entire length. Oppositereduced ends 2I8 and 2I9 of the rod provide shoulders 2I6 and 2I'i whichabut the valve balls in such a position that both balls are held out ofcontact with their seats in the position of the rod 2I5 illustrated inFig. 10. The reduced diameter ends of the rod 2I5 extend throughdiametral openings in the balls, partly to provide supports forrespective ends of rod and ball centering springs 220 and 22I. Thecentering springs are very light in comparison to the centering springsfor the piston, but the light springs are also of substantially equallength and scale in order to center the ball and rod assembly.

To operate the piston 200, the lower side of both the cylinder sleeveI92 and the housing I88 are open as at 222 and adjacent the opening areduced diameter central portion of the piston between the lands isprovided with rack teeth 223. The rack teeth continuously mesh with apinion 224 supported on a horizontal shaft 225, suitably journalled inthe housing I88 as shown in Fig. 11. The shaft is suitably keyed as byflutes or serrations to the pinion 224 and the outwardly proiecting endof the shaft carries the actuator handle 60. The handle 60 is verticalin the neutral position of the actuator piston 200. 1

In operation, the handle 60 is normally held in its vertical position bythe relatively heavy centering springs 204 and 205. Movement of thehandle in either direction away from sa d central position as to thefull line or broken line positions shown on Fig. 2 effects movement ofthe piston 200 in the selected direction for operation of the ring cams56 and 51 of the propeller control mechanism. Movement of the piston 200to the left, Fig. 2 (right, Fig. 10), as by turning of the arm towardthe broken line illustrated position, Fig. 2, traps fluid in thepressure chamber I81 when the piston land The operation also causesclosing movement of the check valve 2I3 due to the fact that the springs22'! and 22I continue to center the ball and rod assembly 2I2, 2l3 and2I5. Thereupon, the trapped charge of fluid in the chamber I 8! movesthrough the supply line 51a to the associated servomotor I83 to move thering cam 56 to operating position. An opposite movement of the piston200 (right, Fig. 10) obviously operates the ring cam 57 as will bereadily apparent.

In order to release the operating ring cam and allow it to he returnedto initial position as by contact with the actuating stems of theoperating pump and/or valve assemblies of units and 3i, the operatormerely releases the handle 60 and the compressed high rate centeringspring returns the piston and the arm to the centered positionillustrated in Fig. 10. Since the centering springs 220 and 22! of theball check valves 2E2 and 2I3 are relatively weak, the .ball ZIZ or 253which sealed its center port leading through the piston will be openedby inertia so. that fluid is free to pass from one pressure chamber tothe other as soon as the operator releases the handle 60.

The separate means for operating the pitch limit latch releasing ringcam is a vertical 14 piston 230 slidable in a sleeve 23I in a verticalbore 232 of the housing I88. The piston'230 has its upper end normallyheld in position to unseal lateral inlet ports 234 of the sleeve 23Ileading to the supply chamber 2I5 as through a cross passage 235 in thehousing. The piston 230 is held in the illustrated position by a spring236 acting directly against the top end of the piston 230 at its lowerend and seated against a socket in an outlet fitting 231 of the housingto which the fluid line 55a is connected. Normally balancing the spring236 to hold the piston 230 normally in its illustrated position, thelower end of the piston 230 has an axial closed socket 238 whichreceives the upper end of a coil spring 239. The lower end of the coilspring 230 bears against a cross head 240 slidable in the lower endportion of the cylinder sleeve 23I and resting against a rotatablymounted operating cam 242. The cross head 240 has an axially ventedsocket 263 which receives and supports the lower end of the coil spring239. The cam 242 preferably comprises a metal disc of generally circularform but provided with opposite flat surfaces at 244 and 24.5, apartabout an eccentric supporting shaft 246 keyed to the cam as byserrations at 25!. The shaft is suitably journalled as at 248 and 249 inspaced portions of the housing I88.

When the operating handle 6| of the pitch limit latch release actuatormechanism is in the position illustrated in Fig. 2, the flat surface 244(Fig. 12) is in contact with the lower end of the cross head 240, thusretaining the cam and handle 6! in the positions illustrated in Figs. 11and 12. When the handle 6! is movedthro-ugh 18 in either direction, thecross head 240 is raised until finally the flat surface 245 is moved incontact with the lower end of the cross head. That operation results incompressing the coil spring 239, overccming the counter-pressure of thespring 236 and raising of the piston 230 to out ofi the inlet ports 234and move the trapped fluid in the upper end of the cylinder 23I to theservomotor of the intermediate ring cam 55. That causes initiation ofoperation of the pitch limit release latch 43 of Figs. 3 and 7.

The cooperating flat surface 245 of the cam 2 32 and the lower flat faceof the cross head 246 hold the cross head 240 in its raised position andmaintain pressure on the piston operating spring 230. Because of theyielding connection between the cross head and the piston 230, thepiston cannot block the cam 242 in its movement toward piston actuatingposition, even though the pressure chamber spaces and connectingdelivery line 55a are of insufiicient capacity to receive the volume offluid attempted to be forced thereto. Because of the possibility ofleakage in the pressure chambers of the pitch limit latch releaseactuator system, the mechanism is so designed as to provide someover-delivery of fluid to the servomotor of the sliding cam 55b, but nomatter how much provision for over-delivery is made'in order to insureimmediate response of the pitch limit latch release servomotor, thecross head 240 can always be moved to its acting position where it isretained by the cooperating flat surfaces 245 of the cam and the fiatbottom end of the cross head 249.

A further feature of the construction shown by I :rshown, the shaft 225has a peripheral groove at 255 rand vertically aligned therewith theshaft 246 has a peripheral groove 256. Formed adjacent and intersectingthe two grooves the housing I88'has a vertical bore 251 which receives asecur- "ing key tangent to the peripheral grooves of the two shafts andoccupying said grooves. The key may be formed simply as a short sectionof 'wire (not shown) held in position by a cap screw 258 in the lowerend of the bore 251.

I claim:

1. In a controllable pitch propeller, a pitch adjustable blade, twosimultaneously and oppositely acting blades adjusting power mechanismsand means turned by said mechanisms to change the pitch of the blade,all rotatable with I the propeller, a fluid'operated actuating mechanismincluding servomotors respectively operable to cause operation of theblade" adjusting means, said actuating mechanism including a doubleended piston and cooperating cylinder "means forming pressure chambersconnected with respective servomotors, said piston being movablemanually in opposite directions from a neutral position, spring meansarranged to re-' turn the piston to neutral position after movement ineither direction, and a by-pass valve "system capable of communicatingsaid pressure chambers, said system including spring means maintainingthe by-pass open in the neutral position of the piston but closing theby-pass whenever the piston is moved in either direction from thatposition.

2.1m a controllable pitch propeller, a pitch adjustable blade,simultaneously and oppositely acting blade adjusting power mechanismsand means turned by said mechanisms to change the pitch of the blade,all rotatable with the propellr, a fluid operated actuating mechanismincluding servomotors respectively operable to- "cause operation of theblade adjusting means,

said actuating mechanism including a double ended piston and cooperatingcylinder means 'forming pressure chambers connected with respectiveservomotors, said piston being movable manually in opposite directionsfrom a neutral position, spring means arranged to return the piston toneutral position after movement in either direction, and a by-pass valvesystem in a through passage of the piston capable of communicating saidpressure chambers through the piston, said system including spring meansmaintaining the through passage open in the neutral position of thepiston but closing the passage whenever the piston ismoved in eitherdirection from that position.

3. In a rotary assembly, a reversible hydraulic motor, two alternatelyacting pumps each supplying a respective pressure chamber of the motor,

non-rotating means operable selectively to actuate the pumps duringrotation of the assembly, a. non-return valve between each pump and themotor pressure chamber supplied thereby, plungers supporting respectivenon-return valves, each plunger being movable by a predetermined backpressure from its connected motor chamber to cause the associatednon-return valve to be opened, and cooperating fluid passage means so:arranged that the non-return valve connected to onemotor chamber can beforced open by exhaust fluid from the motor while the other motorchamber is being supplied by its pump.

- plug then to be moved to openposition; and oooperating fluid passagemeans so arranged that the non-return valve mechanism connected to onemotor pressure chamber can operate as an exhaust valve for that chamberwhile the other motor chamber is being supplied by its pump.

5. In a' rotary assembly, means rotatable with the assembly and forminga hydraulic fluid supply chamber, a pump including a pressure chamberand a reciprocatable piston therein operable to open the pump pressurechamber to the supply chamber on each return stroke of the piston, meansto reciprocate the piston during and as a result of rotation of theassembly, a motor having a fiuid connection with the pump pressurechamber, said connection including a non-return"'valve, and a vacuumbreaker valve in the piston between the pump pressure chamber and thesupply chamber and operating oppositely of the non-return valveon thereturn stroke of the piston.

COLUMBUS R. SACCHINI.

REFERENCES CITED The following references are of record in'the file ofthis patent:

UNITED STATES PATENTS Number Name Date 65,435 Richter June4, 18671,705,293 Horthy et 'al Mar. 12, 1929 1,803,858 MacClatchie May 5, 19311,972,462 Schafer Sept. 4, 1934 1,980,617 Engel Nov. 13, 1934 1,987,651Wiegand Jan. 15,1935 2,023,785 Hoover Dec. 10, 1935 2,057,934 Brown Oct.20, 1936 2,146,030 Schiohn Feb. 7, 1939 2,178,061 Bachman et al Oct. 31,1939 2,190,228 Bowen Feb. 13, 1940 2,207,635 Nardone July 9, 19402,214,257 Pfauser Sept. 10, 1940 2,282,297 Keller May 5, 1942 2,296,288Martin Sept. 22, 1942 2,333,316 Klossner Nov. 2, 1943 2.343,416 KellerMar. 7, 1944 2,357,386 Dick Sept. 5, 1944 2,403,532 Hoover July 9, 19462,422,966 Hoover June 24, 1947 2,433,990 Hardy Jan. 6, 1948 2,491,375Hardy Dec. 13, 1949 2,515,037 Hardy July 11, 1950 FOREIGN PATENTS NumberCountry Date 18,445 Great 'Britain 1897 369,761 Great Britain Mar. 31,1932 464,203 Great-Britain Apr. 12, 1937

